"I want to see and understand the world outside. I don't want to die inside these walls without knowing what's out there!"

Eren possesses great amounts of selflessness, perseverance, fortitude, and a vigorous determination; managing to graduate fifth in his class despite his lack of natural talent. He greatly appreciates and/or admires his comrades, and will swiftly fly into a rage if one of them is injured or killed in front of him. He prizes human life, but his personal sense of justice dictates that anyone who steals away the freedom and dreams of others deserves to die. Whilst assuming his Titan form, Eren seems to become more savage, bloodthirsty, and all-around uncontrollable. Though he is able to consciously control his Titan body after the struggle for Trost, he can very easily become caught up in the pleasure of slaughtering his enemies, indulging in thoughts so brutal he gives the impression of being insane.

Otaku Trivia:

1) He has the highest Titan kill record by far of all the former graduates of the 104th Cadet Corps, though he has killed only one Titan in human form with his ODM abilities, and the rest have been killed using his Titan abilities. In human form, the most kills belong to Mikasa.

2) Hajime Isayama stated in an interview that he based Eren's Titan form off of the Japanese martial artist Yūshin Okami, paraphrasing it to be the "ideal physique of a middleweight mixed martial artist".

3) In the anime, Eren's Titan form has nictitating membranes (a third eyelid possessed by predatory species such as sharks, birds of prey, and reptiles); it can be observed blinking them several times in episode 8. it is unknown whether it possesses this trait in the manga.